Garner State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Garner State Park clear sky chart from 2005-11-06 to 2025-10-04.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	14% 6% 2 5% 3 4 4 3 5% 7% 49%	126324
	Night	14% 5% 2 4 3 3 3 3 5% 7% 52%	123351
Transparency	Day	35% 3 9% 21% 19% 12%	130183
	Night	32% 4 10% 20% 19% 15%	127555
Seeing	Day	15% 7% 23% 31% 20% 4	15969
	Night	16% 6% 24% 37% 15% 1	25865

By Month

Percentage Cloud Cover SE (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	14% 6% 1 4 2 2 3 2 3 5% 59%	4077
	11th to 20th	Day	11% 7% 2 4 3 2 3 3 5% 6% 56%	4287
	21st to end	Day	22% 7% 1 3 3 2 3 3 4 6% 47%	4994
February	1st to 10th	Day	15% 8% 2 5% 3 3 2 3 4 5% 50%	2000
	11th to 20th	Day	18% 7% 2 5% 4 3 3 3 5% 5% 47%	1949
	21st to end	Day	15% 6% 1 4 2 3 4 3 4 6% 53%	1650
March	1st to 10th	Day	14% 6% 2 4 3 3 3 2 3 6% 56%	4645
	11th to 20th	Day	17% 7% 2 5% 3 3 2 2 3 4 53%	4980
	21st to end	Day	16% 7% 2 4 3 3 3 3 5% 6% 49%	5462
April	1st to 10th	Day	15% 7% 1 5% 4 3 3 4 5% 6% 47%	2200
	11th to 20th	Day	17% 5% 2 5% 4 3 3 3 5% 7% 47%	2364
	21st to end	Day	17% 6% 2 4 4 4 3 3 4 5% 47%	2404
May	1st to 10th	Day	21% 7% 2 6% 3 4 4 3 5% 6% 38%	5862
	11th to 20th	Day	12% 4 2 5% 4 3 4 3 5% 9% 49%	5862
	21st to end	Day	15% 8% 2 7% 5% 5% 5% 3 6% 8% 36%	6434
June	1st to 10th	Day	8% 4 1 4 4 4 4 3 6% 10% 50%	2600
	11th to 20th	Day	9% 5% 2 5% 4 4 6% 5% 6% 8% 47%	2600
	21st to end	Day	10% 5% 2 6% 5% 5% 7% 5% 7% 9% 39%	2600
July	1st to 10th	Day	17% 7% 2 6% 4 5% 4 4 5% 8% 38%	5900
	11th to 20th	Day	10% 4 2 5% 4 5% 5% 4 7% 9% 45%	5900
	21st to end	Day	8% 5% 2 6% 4 4 5% 4 7% 10% 46%	6298
August	1st to 10th	Day	2 2 1 3 3 3 3 3 5% 8% 68%	3905
	11th to 20th	Day	4 3 1 3 3 4 4 3 6% 9% 61%	3846
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 6% 9% 50%	4296
September	1st to 10th	Day	12% 6% 2 7% 6% 5% 5% 4 5% 7% 40%	2200
	11th to 20th	Day	11% 6% 2 6% 4 5% 5% 4 6% 7% 43%	2200
	21st to end	Day	10% 4 2 6% 4 4 4 4 6% 7% 48%	2200
October	1st to 10th	Day	8% 5% 2 5% 3 3 4 3 5% 7% 55%	2123
	11th to 20th	Day	15% 5% 2 4 3 3 3 3 5% 6% 51%	2085
	21st to end	Day	16% 4 2 4 3 3 3 2 3 4 57%	2090
November	1st to 10th	Day	17% 8% 2 5% 2 4 3 3 4 7% 46%	1892
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 5% 51%	1800
	21st to end	Day	17% 7% 2 5% 3 3 4 2 3 5% 50%	1800
December	1st to 10th	Day	24% 9% 2 6% 4 3 3 2 3 5% 39%	2940
	11th to 20th	Day	18% 8% 2 6% 4 4 3 2 4 5% 44%	3391
	21st to end	Day	14% 6% 1 3 2 2 2 2 3 4 60%	4488
January	1st to 10th	Night	14% 4 2 3 2 2 3 2 3 7% 58%	5888
	11th to 20th	Night	11% 3 1 3 2 2 2 2 5% 6% 64%	5734
	21st to end	Night	27% 6% 2 4 2 2 2 2 3 4 44%	5984
February	1st to 10th	Night	14% 7% 1 4 2 2 3 2 5% 5% 56%	2400
	11th to 20th	Night	17% 6% 2 5% 2 2 2 3 4 5% 52%	2338
	21st to end	Night	15% 5% 2 4 4 3 3 2 4 7% 50%	1980
March	1st to 10th	Night	12% 7% 2 4 3 3 3 3 5% 7% 51%	5219
	11th to 20th	Night	14% 6% 2 5% 3 3 3 2 3 5% 55%	4980
	21st to end	Night	17% 8% 2 4 3 2 3 2 4 5% 50%	5467
April	1st to 10th	Night	12% 6% 2 4 4 3 3 3 5% 7% 52%	2200
	11th to 20th	Night	16% 6% 2 5% 3 4 3 3 5% 5% 48%	1980
	21st to end	Night	19% 6% 2 5% 4 3 3 3 4 5% 47%	1995
May	1st to 10th	Night	23% 8% 3 5% 3 3 3 3 4 5% 42%	4053
	11th to 20th	Night	9% 4 2 4 3 3 3 3 5% 9% 54%	4053
	21st to end	Night	14% 6% 2 5% 4 4 4 4 6% 10% 41%	4443
June	1st to 10th	Night	5% 3 1 3 3 4 3 4 6% 9% 60%	1800
	11th to 20th	Night	7% 4 1 4 3 4 4 4 5% 8% 57%	1800
	21st to end	Night	9% 5% 2 4 4 4 3 4 5% 10% 51%	1800
July	1st to 10th	Night	14% 6% 2 5% 4 4 4 4 6% 9% 43%	4078
	11th to 20th	Night	7% 5% 2 5% 4 4 4 4 6% 9% 51%	4077
	21st to end	Night	10% 6% 2 5% 3 4 4 4 6% 9% 49%	4554
August	1st to 10th	Night	1 1 2 2 2 3 3 5% 8% 72%	3255
	11th to 20th	Night	3 2 1 3 3 3 3 3 6% 10% 62%	3213
	21st to end	Night	6% 4 2 4 3 4 4 4 7% 10% 52%	3597
September	1st to 10th	Night	10% 6% 2 6% 4 5% 4 3 6% 9% 45%	2200
	11th to 20th	Night	11% 6% 2 5% 4 4 4 3 5% 9% 48%	2200
	21st to end	Night	9% 4 2 5% 4 3 5% 5% 6% 8% 51%	2200
October	1st to 10th	Night	9% 4 1 4 3 2 3 2 4 7% 61%	2123
	11th to 20th	Night	14% 5% 2 4 2 3 3 2 4 6% 56%	2090
	21st to end	Night	14% 4 1 3 2 2 1 2 2 4 65%	2491
November	1st to 10th	Night	15% 6% 2 4 3 2 3 2 4 5% 54%	2403
	11th to 20th	Night	11% 6% 2 4 3 3 2 3 5% 5% 57%	2600
	21st to end	Night	17% 5% 1 4 3 3 3 3 4 6% 51%	2600
December	1st to 10th	Night	25% 7% 2 4 3 3 4 3 4 5% 39%	4250
	11th to 20th	Night	21% 6% 2 4 3 3 3 2 3 4 49%	4816
	21st to end	Night	16% 5% 1 3 1 2 2 2 3 5% 58%	6490

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	32% 1 2 19% 26% 19%	4078
	11th to 20th	Day	31% 2 3 16% 25% 23%	4287
	21st to end	Day	42% 1 4 13% 26% 14%	4994
February	1st to 10th	Day	39% 2 5% 14% 21% 19%	2000
	11th to 20th	Day	41% 2 4 18% 21% 14%	1959
	21st to end	Day	35% 2 7% 17% 21% 19%	1650
March	1st to 10th	Day	34% 1 5% 16% 17% 27%	4645
	11th to 20th	Day	38% 1 3 10% 14% 34%	4980
	21st to end	Day	38% 2 6% 18% 19% 17%	5464
April	1st to 10th	Day	38% 3 7% 17% 18% 16%	2200
	11th to 20th	Day	38% 2 6% 22% 16% 16%	2364
	21st to end	Day	41% 3 7% 19% 17% 13%	2404
May	1st to 10th	Day	46% 4 8% 18% 15% 8%	5900
	11th to 20th	Day	33% 3 11% 19% 22% 12%	5866
	21st to end	Day	45% 4 9% 25% 15% 2	6447
June	1st to 10th	Day	29% 4 14% 30% 19% 4	2600
	11th to 20th	Day	33% 5% 11% 27% 18% 6%	2600
	21st to end	Day	37% 6% 13% 24% 15% 4	2600
July	1st to 10th	Day	43% 5% 17% 27% 8% 1	5836
	11th to 20th	Day	34% 6% 16% 31% 12% 1	5831
	21st to end	Day	31% 6% 18% 25% 18% 2	6118
August	1st to 10th	Day	14% 4 12% 43% 27% 1	3892
	11th to 20th	Day	19% 4 22% 41% 12% 2	3882
	21st to end	Day	27% 6% 17% 26% 21% 2	4295
September	1st to 10th	Day	41% 6% 11% 19% 17% 7%	2200
	11th to 20th	Day	38% 5% 11% 23% 17% 5%	2200
	21st to end	Day	34% 5% 10% 21% 19% 12%	2200
October	1st to 10th	Day	18% 3 6% 14% 25% 35%	3513
	11th to 20th	Day	32% 3 6% 16% 19% 24%	3441
	21st to end	Day	30% 3 4 16% 35% 12%	3428
November	1st to 10th	Day	40% 3 7% 20% 19% 11%	1892
	11th to 20th	Day	36% 3 6% 18% 20% 17%	1800
	21st to end	Day	41% 2 4 19% 20% 14%	1800
December	1st to 10th	Day	52% 2 5% 14% 17% 10%	2940
	11th to 20th	Day	44% 3 6% 15% 18% 15%	3389
	21st to end	Day	31% 2 3 16% 29% 20%	4488
January	1st to 10th	Night	31% 2 5% 17% 26% 19%	5888
	11th to 20th	Night	23% 2 4 18% 26% 27%	5734
	21st to end	Night	46% 1 3 11% 21% 17%	5984
February	1st to 10th	Night	32% 3 6% 15% 22% 23%	2400
	11th to 20th	Night	36% 2 5% 19% 20% 18%	2338
	21st to end	Night	36% 2 6% 16% 21% 20%	1980
March	1st to 10th	Night	35% 3 7% 18% 17% 20%	5219
	11th to 20th	Night	34% 2 6% 13% 15% 31%	4980
	21st to end	Night	38% 2 8% 19% 17% 16%	5467
April	1st to 10th	Night	33% 3 11% 18% 17% 19%	2200
	11th to 20th	Night	39% 3 9% 16% 16% 18%	1980
	21st to end	Night	41% 3 9% 18% 16% 14%	1995
May	1st to 10th	Night	44% 5% 8% 17% 14% 12%	4080
	11th to 20th	Night	30% 3 13% 20% 21% 14%	4054
	21st to end	Night	39% 4 14% 26% 13% 4	4452
June	1st to 10th	Night	21% 5% 18% 33% 21% 3	1800
	11th to 20th	Night	25% 5% 13% 29% 23% 6%	1800
	21st to end	Night	28% 7% 20% 26% 16% 4	1800
July	1st to 10th	Night	37% 8% 22% 26% 6% 1	4035
	11th to 20th	Night	28% 8% 21% 29% 13% 1	4026
	21st to end	Night	30% 6% 21% 26% 14% 2	4423
August	1st to 10th	Night	10% 5% 16% 43% 25% 1	3244
	11th to 20th	Night	19% 5% 28% 37% 10% 2	3243
	21st to end	Night	26% 8% 20% 27% 17% 2	3597
September	1st to 10th	Night	35% 6% 13% 22% 17% 7%	2200
	11th to 20th	Night	33% 7% 17% 22% 16% 6%	2200
	21st to end	Night	30% 5% 12% 23% 18% 12%	2200
October	1st to 10th	Night	17% 3 7% 16% 22% 36%	3513
	11th to 20th	Night	27% 3 7% 13% 26% 24%	3460
	21st to end	Night	25% 2 5% 17% 36% 16%	4103
November	1st to 10th	Night	35% 2 6% 19% 23% 15%	2403
	11th to 20th	Night	30% 3 7% 20% 21% 19%	2600
	21st to end	Night	36% 2 7% 17% 20% 17%	2600
December	1st to 10th	Night	49% 2 8% 14% 14% 14%	4250
	11th to 20th	Night	41% 2 5% 14% 20% 18%	4817
	21st to end	Night	31% 2 4 16% 27% 20%	6490

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	21% 9% 36% 25% 9%	300
	11th to 20th	Day	22% 15% 29% 23% 10% 1	300
	21st to end	Day	22% 12% 33% 25% 8%	330
February	1st to 10th	Day	28% 10% 25% 26% 10% 1	300
	11th to 20th	Day	25% 11% 36% 21% 6% 1	300
	21st to end	Day	23% 12% 42% 19% 4	249
March	1st to 10th	Day	23% 16% 38% 20% 3	300
	11th to 20th	Day	22% 14% 43% 17% 4	300
	21st to end	Day	22% 13% 42% 20% 3	330
April	1st to 10th	Day	21% 14% 38% 24% 3	300
	11th to 20th	Day	15% 18% 40% 23% 4	482
	21st to end	Day	15% 15% 43% 21% 5%	504
May	1st to 10th	Day	21% 11% 35% 26% 7%	703
	11th to 20th	Day	21% 7% 34% 28% 8% 1	725
	21st to end	Day	20% 7% 30% 32% 10%	789
June	1st to 10th	Day	8% 4 20% 46% 20% 2	730
	11th to 20th	Day	11% 3 20% 48% 17% 2	730
	21st to end	Day	12% 3 15% 35% 29% 6%	730
July	1st to 10th	Day	17% 3 10% 32% 31% 7%	721
	11th to 20th	Day	8% 1 5% 37% 42% 6%	718
	21st to end	Day	6% 1 7% 36% 43% 7%	745
August	1st to 10th	Day	2 5% 41% 42% 10%	527
	11th to 20th	Day	7% 1 7% 32% 43% 10%	517
	21st to end	Day	7% 1 7% 31% 40% 13%	580
September	1st to 10th	Day	10% 1 9% 29% 38% 13%	330
	11th to 20th	Day	7% 1 8% 27% 41% 15%	330
	21st to end	Day	9% 3 7% 28% 43% 10%	330
October	1st to 10th	Day	9% 3 13% 37% 30% 8%	309
	11th to 20th	Day	13% 4 16% 45% 20% 2	300
	21st to end	Day	21% 11% 24% 26% 16% 2	330
November	1st to 10th	Day	24% 4 26% 30% 14% 2	300
	11th to 20th	Day	21% 9% 24% 31% 12% 4	300
	21st to end	Day	24% 11% 32% 22% 8% 2	300
December	1st to 10th	Day	21% 9% 27% 26% 15% 2	300
	11th to 20th	Day	24% 13% 29% 22% 11% 1	300
	21st to end	Day	21% 8% 32% 26% 12% 1	330
January	1st to 10th	Night	17% 9% 27% 38% 9% 1	1000
	11th to 20th	Night	20% 9% 27% 36% 8%	925
	21st to end	Night	24% 8% 27% 33% 8%	880
February	1st to 10th	Night	22% 10% 27% 34% 7% 1	800
	11th to 20th	Night	23% 11% 29% 30% 6%	784
	21st to end	Night	21% 10% 37% 30% 2	660
March	1st to 10th	Night	22% 11% 34% 28% 4 1	736
	11th to 20th	Night	19% 11% 35% 30% 5%	600
	21st to end	Night	17% 10% 43% 25% 5%	660
April	1st to 10th	Night	14% 12% 41% 30% 2	600
	11th to 20th	Night	19% 13% 42% 24% 2	593
	21st to end	Night	20% 12% 40% 25% 3	600
May	1st to 10th	Night	18% 11% 39% 29% 4	600
	11th to 20th	Night	18% 7% 35% 34% 6%	591
	21st to end	Night	17% 7% 35% 33% 8%	650
June	1st to 10th	Night	6% 3 30% 46% 15%	600
	11th to 20th	Night	9% 3 31% 48% 10%	600
	21st to end	Night	9% 4 21% 46% 19% 1	600
July	1st to 10th	Night	13% 2 12% 50% 22% 1	585
	11th to 20th	Night	6% 2 13% 49% 30% 2	582
	21st to end	Night	7% 2 10% 47% 33% 2	657
August	1st to 10th	Night	1 1 9% 48% 40% 1	597
	11th to 20th	Night	5% 1 7% 49% 35% 2	594
	21st to end	Night	7% 1 10% 41% 38% 3	660
September	1st to 10th	Night	9% 1 11% 42% 35% 3	600
	11th to 20th	Night	12% 1 7% 42% 36% 2	600
	21st to end	Night	10% 1 14% 38% 33% 4	600
October	1st to 10th	Night	8% 3 11% 47% 28% 2	579
	11th to 20th	Night	16% 3 19% 39% 21% 1	570
	21st to end	Night	15% 6% 23% 32% 22% 3	819
November	1st to 10th	Night	18% 5% 17% 37% 20% 2	843
	11th to 20th	Night	14% 6% 21% 40% 17% 2	1000
	21st to end	Night	21% 8% 22% 35% 13% 1	1000
December	1st to 10th	Night	19% 6% 23% 37% 13% 2	1000
	11th to 20th	Night	24% 9% 22% 34% 10%	1000
	21st to end	Night	20% 8% 24% 39% 9% 1	1100

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